1. Field Of the Invention
The present invention relates to a novel alkaline lipase, method for producing the same, a microorganism producing the lipase and use thereof. More particularly, the present invention relates to a novel lipase having an optimum pH in an alkaline region and being produced by a bacteria belonging to the genus Pseudomonas, method for producing the same, a microorganism producing the same, and a detergent composition containing an enzyme which can hydrolyze lipids in an alkaline pH range, wherein the aqueous solution of said detergent composition has an alkaline pH upon washing.
2. Description Of Related Art
Lipase is used widely as a food processing enzyme for forming flavor of milk products, as a medical enzyme for a digestive, as a diagnostic enzyme for the determination of blood lipid, as an industrial enzyme for the hydrolysis or modification of oils and fats, and so on.
Recently, attention has been paid to the use of lipase as an additive to detergent compositions. It has been known to blend a protease with a detergent composition in order to decompose and remove proteins or the like soil attached to things to be washed. It has also been known to blend a cellulase with a detergent composition in order to remove soil attached to cellulose fiber articles to be washed, or blend a saccharide hydrolyzing enzyme such as an amylase with a detergent composition in order to decompose and remove a saccharide or the like soil attached to an article to be washed. Further, recently, it has been known to blend a lipase with a detergent composition to decompose and remove lipids attached to an article to be washed so that washing efficiency can be increased. This use is described in a report by H. Andree et al., "Lipase as Detergent Components," (Journal of Applied Biochemistry, 2, 218-229 (1980)).
Preferred lipase to be blended with detergent compositions includes alkaline lipases which function at alkaline pH values since the pH of a washing solution is in an alkaline pH range under ordinary washing conditions. In addition, it has been known that while lipid stains can generally be removed relatively readily at high temperatures and under high alkaline conditions, lipid stains cannot be removed sufficiently with washing at low temperatures (60.degree. C. or lower). There has been observed an increasing tendency of washing at a lower temperature not only in Japan where mainly low temperature washing has been performed but also in European countries and U.S.A., and hence preferred lipases to be blended with detergent compositions are those which can act sufficiently at low temperatures. Also, preferred lipases to be blended with detergent compositions are those which can exhibit their function stably upon washing in the presence of detergent components such as a surfactant, and protease that is present in various detergents, or those which is less inhibited by detergent components such as a surfactant, and which are stable when stored as a blend with the detergent composition. There has been a keen desire for the development of a detergent composition which contains a lipase having the aforementioned preferred characteristics and which has a high washing efficacy against lipid soils.
It has been known that microorganisms producing lipases include those belonging to the genera Pseudomonas, Alcaligenes, Achromobacter, Mucor, Candida, Humicola, etc. Most of the lipases produced by these microorganisms have optimum pH values in a range from neutral to a weakly alkaline region, and exhibit poor stability to anionic surfactants. Further, the lipase activity of lipases produced by the microorganisms belonging to the genera Achromobacter, Candida, Mucor, and Humicola is inhibited strongly in copresence of anionic surfactants, respectively.
It has been well known that microorganisms belonging to the genus Pseudomonas produce a lipase. The genus Pseudomonas include various species such as Pseudomonas fluorescens, Pseudomonas cepacia, Pseudomonas fragi, Pseudomonas alcaligenes, Pseudomonas aeruginosa. However, known lipases produced by these specified species do not meet the aforementioned characteristics.
Furthermore, productivity of lipase by conventional lipase-producing strains was generally low and hence insufficient for industrial application. In order to solve this problem, it is a usual course to try to improve productivity by means of mutation. Conventional method for improving productivity is to perform a mutational treatment to strains, and select those strains having higher productivity from among all the surviving strains. This conventional method takes a long time and much labor. Therefore, it has been desired strongly to establish a method of producing lipases more efficiently. While for other enzymes, there have been known methods of producing cellulases, proteases or amylases efficiently using strains resistant to Vancomycin or Ristocetin (Japanese Patent Application Laid-Open No. 222771/1989), and a method of producing an .alpha.-amylase using a strain resistant to Tunicamycin (T. Sasaki, et al., BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, 70, 125-131, 1976), no report has been made on lipases.